Half-tone screen.



No. 725,252. PATENTED APR. 14, 1903. J. JAGOBSON.

HALF-TONE SCREEN.

APPLICATION FILED MAR. @1902.

N0 MODEL.

TNE no ms PETERS co. moTau-rwo WASHINGTON. n. c

JOHN JAOOBSON, OF NEW YORK, N. Y., ASSIGNOR TO IDA.M. CRAWFORD, OF NEWYORK, N. Y.

B-IALFMTOINE sonnets.

SPECIFICATION forming part of Letters Patent No. 725,252, dated April14, 1903. Application filed March 5, 1902. Serial No. 96,752. (Nomodel.)

To alt whom, it may concern:

Be it known that I, JOHN JAOOBSON, of New York, county of New York, andState of New York,haveinvented an Improvement in Half- Tone Screens, ofwhich the following description, in connection with the accompanyingdrawings, is a specification, like letters on the drawings representinglike parts.

The presentinvention relates to a half-tone screen for use in makinghalf-tone negatives, the object of the invention being to obtain ascreen of such character that by consecutive exposures, qualified byvariations in the diaphragm, a greater contrast can be obtained in theprinting-plate finally obtained from the half-tone negative.

The screen embodying the invention is provided with the usualregularly-spaced lines, with the addition, however, ofsymmetricallyarranged parts having a greater area of opacity than thatof the majority of the lines, these parts of greater area of opacitypreferably, though not essentially, consisting of dots symmetricallyarranged at the intersections of the lines, the purpose being topreserve certain portions of the printing-surface in the high lights,these portions, however, being lesser in number than the portionspreserved by the intersections of the lines of an ordinary line-screenin producing the halftone plate. Taking, for example, an ordinaryhalf-tone plate, it is of course possible to intensify to some extentthe high lights by a second or prolonged exposure; but the resistanceoffered by the thin lines and their intersecting points would in thisinstance be substantially overcome, so that when a plate made from thenegative were etched that portion of the surface corresponding to thehigh lights would be entirely dissolved away and a half-tone plate inwhich the high-light portions were entirely deprived ofprinting-surfaces would be objectionable, for the reason that therewould be no support for the mate rial upon which the ink would betransferred in printing, so that the lines of demarcation between theshaded portions and the lighted portions would be sharp and smudgy. Itis desirable, therefore, in intensifying the high lights to stillpreserve certain printing portions of the plate for the purpose ofsupporting the material printed upon uniformly over the entire surfaceof the plate. This is accomplished in accordance with the presentinvention, in which those printing portions of the plate whichcorrespond to those parts of the picture where there is practically noshade are modified by lessening the number of printing-surfaces, whichin the print are represented by dots, rather than by eliminating thesaid surfaces altogether. To these ends the screen embodying theinvention is provided with the usual number of regularlyspaced opaquelines, to which are added a lesser number of portions of greater area of6 5 opacity symmetrically spaced and symmetrically arranged withrelation to the lines, so that the nagative can be overexposed to aconsiderable extent,without, however, being chemically changedthroughout the entire surface corresponding to the high lights. In otherwords, the negative can be exposed long enough to overcome theresistance of the thinner lines, While the parts protected by thegreater areas of opacity are not subjected to the chemical change.

Figure 1 is a representation of a line-screen embodying the invention inthe preferred form, and Fig. 2 is a similar view showing a modification.

The screen shown in Fig. 1 is provided with lines a and a preferablyarranged, as shown, at right angles to each other, and the said screenis provided at certain intersections of the lines with enlarged opaqueportions Z), which may be conveniently referred to as dots, with theunderstanding, of course, that it is immaterial what shape these opaqueportions are formed in, a rectangular shape, however, being preferable.These dots are symmetrically arranged, being herein shown as coveringfour out of every nine intersections of the lines, it being obvious,however, that the arrangement may be varied providedthatthearrangementis symmetrical. In pre- 5 paring a plate inconjunction with a screen of this kind it will be seen that if theexposure is first made with a comparatively small diaphragm the moreshaded portions of the plate will be acted upon to the usual ice extent,and the plate can then be subjected to a further exposure with a largerdiaphragm,

the result being that the light will act with full effect upon allportions of the plate exposed to the higher lights except thoseprotected by the enlarged opaque portions or dots I), while this furtherexposure will not materially affect the more shaded portions, but willact to affect the negative, so as to practically eliminate all theprinting-surfaces of the finished half-tone plate in the high lightsexcept those which correspond with the dots b.

In the modification shown in Fig. 2 the screen is shown as provided withsymmetrically-arranged lines 11 which are wider or have a greater areaof opacity than the other lines, so that certain portions of the plateregularly and symmetrically arranged have a greater area of opacity thanthe main portions of the plate. While the screen made in this way maynot be so efiectual as a screen made with the lines and dots, as shownin Fig. 1, it is obvious that upon exposure substantially the sameeffect will be produced,

and it is not, therefore, intended to limit the invention to anyspecific design so far as relates to the opaque portions of the screen,since the design may obviously be modified Without afiecting the resultand without departing from the invention.

I claim 1. A half tone screen having regularlyspaced opaque lines;combined with a lesser number of portions of greater area of opacityalso equally spaced and coincident with the lines of lesser area ofopacity.

2. A half-tone screen having regularlyspaced opaque lines, combined withdots symmetrically arranged at the intersections of some of the lines,substantially as described.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

JOHN JACOBSON.

Witnesses:

JOHN H. WYBURN, HELEN HEROLD.

